System Comprising a Multi-Layer-Multi-Turn Structure for High Efficiency Wireless Communication

ABSTRACT

A structure for wireless communication having a plurality of conductor layers, an insulator layer separating each of the conductor layers, and at least one connector connecting two of the conductor layers wherein an electrical resistance is reduced when an electrical signal is induced in the resonator at a predetermined frequency.

RELATED APPLICATIONS

This application claims the benefit of U.S. application Ser. No.13/255,659 entitled “System and Method for Wireless Power Transfer inImplantable Medical Devices,” filed on Sep. 9, 2011, which claimspriority to International Application No. PCT/US2010/000714 entitled“System and Method for Wireless Power Transfer in Implantable MedicalDevices,” filed on Mar. 9, 2010, which claims priority to U.S.Provisional Application No. 61/158,688, filed on Mar. 9, 2009, thedisclosures of which are entirely incorporated herein by reference.

The present patent application also hereby incorporates by reference theentire contents of U.S. patent application Ser. No. ______, filed onSep. 15, 2011; U.S. patent application Ser. No. ______, filed on Sep.15, 2011; U.S. patent application Ser. No. ______, filed on Sep. 15,2011; U.S. patent application Ser. No. ______, filed on Sep. 15, 2011;U.S. patent application Ser. No. ______, filed on Sep. 15, 2011; U.S.patent application Ser. No. ______, filed on Sep. 15, 2011; U.S. patentapplication Ser. No. ______, filed on Sep. 15, 2011; and U.S. patentapplication Ser. No. ______, filed on Sep. 15, 2011.

TECHNICAL FIELD

The present subject matter generally relates to methods, systems andapparatus to design, operate and manufacture wireless power and/or datatransmission and/or communication systems, and more specifically, tomethods, systems and apparatus to design, operate and manufacture a highefficiency structure for use in near-field wireless power and/or datatransmission and/or communication systems.

BACKGROUND

In recent years, applications employing near-field wireless power and/ordata transmission and/or communication systems, such as commercialelectronics, medical systems, military systems, high frequencytransformers, microelectronics including nanoscale power and/or datatransfer or microelectromechanical systems (MEMS) thereof, industrial,scientific and medical (ISM) band receivers, wireless sensing and thelike, have been limited in achieving optimal performance because theantennas (also referred to as resonators) utilized in these systems haverelatively low quality factors.

The relatively low quality factors of these wireless transmission and/orcommunication systems are mainly due to higher resistive losses causedby a phenomenon known as the “skin effect.” Generally, skin effect isthe tendency of an alternating electric current (AC) to distributeitself within a conductor such that the current density is morepredominant near the surface of the conductor with the remainingconductor body ‘unused’ relative to electrical current flow. Theremaining conductor body is ‘unused’ relative to electrical current flowbecause the current density typically decays with distance therewithinaway from the surface of the conductor. The electric current flowsmostly near the surface, and is referred to as the “skin” of theconductor. The depth at which current flows from the surface is referredto as the “skin depth.” The “skin depth” then defines the electricalsignal conducting path that is active in transmission and/orcommunication, while the conductor is defined as the body that iscapable of conducting an electrical signal.

In systems employing wireless power and/or data transmission and/orcommunication, the skin effect phenomenon generally causes energy lossas current flows through the antenna wire and circuit. Higher resistiveloss at high frequencies is a problem faced by most electronic devicesor appliances. Skin effect becomes more prevalent when operatingfrequency increases. With higher frequencies, current that normallyflows through the entire cross section of the wire forming the antennabecomes restricted to its surface. As a result, the effective resistanceof the wire is similar to that of a thinner wire rather than of theactual diameter through which the current could be distributed. A wireexhibiting tolerable resistance for efficient performance at lowfrequency transitions into a wire of unacceptable resistance at highfrequency. The transition from tolerable to unacceptable resistancetranslates into an inefficient power and/or data transmission and/orcommunication system that is unable to conduct an electrical signal asneeded in particular applications. Additionally, today's antenna designsdo not resolve these inefficiencies, and, in some cases, exacerbate theinefficiencies of a wireless power and/or data transmission and/orcommunication system. Although not exhaustive, typical applicationslimited by current antenna technology include, for example, radiofrequency identification (RFID), battery charging and recharging,telemetry, sensing, communication, asset tracking, patient monitoring,data entry and/or retrieval and the like. Overheating of systemcomponents, rate and accuracy of data retrieval, rate of energydelivery, transmission distance constraints, and transmissionmisalignment limitations are other serious problems in wireless powerand/or data transmission and/or communication applications.

In applications of Implanted Medical Devices (IMDs), such as pacemakers,defibrillators and neuromodulation or neuromuscular stimulation devices,there is a desire to minimize battery recharge time. Faster batteryrecharge time reduces, for example, patient duration of discomfort,inconvenience, and potential for injury. If antennas have less resistivelosses, battery recharge could be accomplished from greater distancesand with higher tolerance to antenna misalignment or disorientationwithout compromising performance. Precise orientation and alignment isknown to be difficult to achieve, especially for obese patients.Additionally, and/or alternatively, if structures of smaller sizes canbe designed and practically manufactured while maintaining theperformance characteristics required for successful system operation,then the overall dimensions of IMD's could be decreased.

In RFID applications, such as supply chain management, productauthenticity, and asset tracking, there is a need to increase readrange, increase read rates, improve system reliability and improvesystem accuracy. At high frequency for example, read range is at mostthree feet which is generally insufficient for pallet tracking. Ultrahigh frequency readers enable greater read distances of eight to tenfeet, however, they introduce other performance issues like signals thatare reflected by metal or are absorbed by water, or display unreadable,null spots in read fields. Increased read range requires concentratedpower to facilitate reflecting back the signal for better performance,hence, a more efficient structure could help solve these issues.

In applications requiring efficient low loss coils which need tomaintain resonance under harsh conditions, conventional wire-basedantennas could be deformed. It is well known that any deformation of thewire cross-section will lead to a change in inductance and possiblyresistance, which in turn will change the resonance frequency of theantenna and consequently may increase overall system resistance.Improved methods of manufacturing these types of structures that reducethe potential for compromising deformation could eliminate this problem.The present teachings include methods of manufacture that include bothrigid structure designs and fixed flexible structure designs.

Litz wires were developed, in part, in an attempt to address the issuesdiscussed above. However, Litz wires are generally insufficient for usein high frequency applications, and are therefore generally not usefulin applications having operating frequencies above about 3 MHz. A Litzwire is a wire consisting of a number of individually insulated magnetwires twisted or braided into a uniform pattern, so that each wirestrand tends to take all possible positions in the cross-section of theentire conductor. This multi-strand configuration or Litz constructionis designed to minimize the power losses exhibited in solid conductorsdue to “skin effect”. Litz wire constructions attempt to counteract thiseffect by increasing the amount of surface area without significantlyincreasing the size of the conductor. However, even properly constructedLitz wires exhibit some skin effect due to the limitations of stranding.Wires intended for higher frequency ranges generally require morestrands of a finer gauge size than Litz wires of equal cross-sectionalarea but composed of fewer and larger strands. The highest frequency atwhich providers of Litz wires offer configurations capable of improvingefficiencies is about 3 MHz. There is currently no solution forapplications with operating frequencies beyond this 3 MHz maximumfrequency limit.

Hence a need exists for an improved high efficiency structure design andmethod of manufacture that reduces the intrinsic resistive losses of thestructure, and in particular reduces intrinsic resistive losses of thestructure at high frequencies to achieve high quality factors.

SUMMARY

The teachings herein alleviate one or more of the above noted problemsof higher resistive losses at high frequencies resulting in lowerquality factors by utilizing the multi-layer wire concept to increasethe area of conductance within a structure. The multi-layer wireconfiguration results in a reduction of conductor loss and an increasein the qualify factor of the structure. The present teachings apply towireless transmission and/or communication for near-field energytransfer, power transfer, data transfer or combinations thereof. Morespecifically, the present teachings apply to wireless transmissionand/or communication for near-field energy networks, power networks ordata networks, including any and all combinations of such networks.

Wireless energy transfer or wireless power transmission is thetransmission of electrical energy from a power source to an electricalload without interconnecting wires. For wireless transmission of energy,power or data, efficiency is a significant parameter, as thetransmission signal must arrive at the receiver or receivers to make thesystem practical. The most common form of wireless transmissioninvolving energy, power, or data transfer is carried out using directinduction followed by resonant magnetic induction. Other methodscurrently being considered include electromagnetic radiation, forexample but not limited to, microwaves or lasers.

In addition, wireless energy reception or wireless power reception isthe reception of electrical energy from a power source withoutinterconnecting wires. For wireless reception of energy, power or data,efficiency is a significant parameter, as the reception of a signal mustbe received from a transmitter or transmitters to make the systempractical. As such, the forms of wireless reception embodying energy,power or data can be carried out using direct induction, resonantmagnetic induction as well as electromagnetic radiation in the form ofmicrowaves or lasers.

Furthermore, the embodiments of the present invention are capable ofwireless communication of electrical energy, electrical power and/ordata without interconnecting wires. Wireless communication embodies thetransmission and/or reception of electrical energy, electrical power ordata either simultaneously or independently.

One aspect of the present teachings is a resonator for wireless powerand/or data transfer or reception wherein resistive losses within theresonator are minimized by maximizing useful conductor cross-sectionalarea in a wire cross section. In one embodiment, the resonator mitigatesthe unwanted high frequency skin effect by introducing non-conductingdielectric layers within its wire, resulting in a structure thatcomprises layers of conducting material alternating with layers ofnon-conducting material. The structure effectively provides an increasednumber of surfaces each with its characteristic skin depth and allelectrically, or otherwise, connected. The skin depth may range fromapproximately one-half of the conductor depth to about equal to theconductor depth. The conductor depth may be in the range of skin depthto twice the skin depth. However, depending on the available technology,costs, and application, the conductor depth may be as large as twentytimes or more the skin depth.

The resonator includes a coil having at least one turn wherein the coilis made up of a multi-layer wire. The multi-layer wire may include afirst and second conductive layer separated by a layer of insulatingmaterial. The conductive layers may have substantially the samethickness and/or depth, wherein the thickness and/or depth may be in therange of skin depth to twice the skin depth. However, depending on theavailable technology, costs, and application, the conductor thicknessand/or depth may be as large as twenty times or more the skin depth.Each conductive layer may be electrically connected to each other usingat least one method of interconnect, such as but not limited to a via, asolder, a tab, a wire, a pin, or a rivet.

One purpose of the non-conducting layer is to insulate two differentconducting layers. The most basic design of the non-conducting layerwould ideally be as thin as the manufacturing process practicallypermits, while still providing sufficient insulating properties. Forexample, in PCB technology, the thickness of layers is dictated by the“core thickness” and the pre-preg thickness. In another design, thethickness of the non-conducting layer is selected to modify theelectrical behavior of the structure.

The resonator may have a quality factor greater than 100. Preferably,the quality factor is greater than 350. Most preferably, the qualityfactor is greater than 600. It will be apparent to those skilled in theart that systems requiring two resonators may either have resonatorswith equal and even similar quality factors. Also, it will be apparentto one skilled in the art that systems requiring two resonators mayutilize resonators where one resonator has a quality factorsubstantially different from the other. The quality factor selection foreach resonator will depend on the application, the design specificationfor each and the intended use of each resonator. It is understood thattraditional inductively coupled systems utilize resonators with aquality factor around 30. Additionally, it will be apparent to oneskilled in the art that the quality factor of a resonator may bedependent on the environment in which it is used, so, for example, aresonator that has a quality factor of 100 in air, may only have aquality factor of 50 when implanted in human or animal tissue. In anygiven environment, the MLMT structure described herein should outperformtraditional resonators.

As a result, the reduction of losses in the wire and the significantlyreduced internal resistance of the resonator could enable highefficiency, extended range, compact wireless systems that consume lessenergy, have longer run time and simplify operation without compromisingevents like overheating.

In one example, there is disclosed a structure for wireless transmissionor wireless reception. The structure is designed to wirelessly transmitand/or receive electrical energy, electromagnetic energy, and/orelectrical power. In addition, the structure is capable of electronicdata transmission. Furthermore, the structure is capable of transmittingand/or receiving a combination of electrical energy, electromagneticenergy, electrical power and electronic data together or separately.

The structure may comprise a plurality of conductor layers, an insulatorlayer separating each of the conductor layers, and at least oneconnector connecting two or more of the conductor layers. Each of theplurality of conductor layers may have at least one turn and may furtherbe placed in a parallel orientation. Each conductor layer may be formedfrom an electrically conductive material. The electrically conductivematerial may be comprised of copper titanium, platinum andplatinum/iridium alloys, tantalum, niobium, zirconium, hafnium, nitinol,Co—Cr—Ni alloys, stainless steel, gold, a gold alloy, palladium, carbon,silver, a noble metal or a biocompatible material and any combinationthereof. The conductor layer may have a cross-sectional shape, such as,but not limited to, a circular cross-section, a rectangularcross-section, a square cross-section, a triangular cross-section, or anelliptical cross-section. The connector connecting the conductor layersmay be but is not limited to a via, a solder, a tab, a wire, a pin, or arivet.

The structure may have structural shape, such as but not limited to acircular solenoidal configuration, a square solenoidal configuration, acircular spiral configuration, a square spiral configuration, arectangular configuration, a triangular configuration, a circularspiral-solenoidal configuration, a square spiral-solenoidalconfiguration, and a conformal solenoid configuration. Otherconfigurations may be used to modify the electrical properties of thestructure.

An electrical resistance in the structure may be reduced when anelectrical signal is induced in the resonator at a frequency. Thefrequency may be selected from a frequency range from about 100 kHz toabout 10 GHz. Further, the frequency may be a frequency band that rangesfrom or is within about 100 kHz to about 10 GHz. The electrical signalmay be an electrical current, an electrical voltage, a digital datasignal or any combination thereof.

In another example, there is disclosed a resonator for wirelesstransmission or wireless reception. The resonator is designed towirelessly transmit and/or receive electrical energy, electromagneticenergy, and electrical power. In addition, the resonator is capable ofelectronic data transmission or reception. Furthermore, the resonator iscapable of transmitting and/or receiving a combination of electricalenergy, electromagnetic energy, electrical power and electronic datatogether or separately.

The resonator may comprise a plurality of conductors, each conductorhaving a conductor length, a conductor height, a conductor depth, and aconductive surface having a skin depth. The skin depth may range fromapproximately one-half of the conductor depth to about equal to theconductor depth. The conductor depth may be in the range of skin depthto twice the skin depth. However, depending on the available technology,costs, and application, the conductor depth may be as large as twentytimes or more the skin depth. The plurality of conductor layers may haveat least one turn. Further, each of the plurality of conductor layersmay or may not have substantially the same conductor length, conductorheight, or conductor depth. The conductor layers may be formed from anelectrically conductive material. The electrically conductive materialmay be comprised of copper, titanium, platinum and platinum/iridiumalloys, tantalum, niobium, zirconium, hafnium, nitinol, Co—Cr—Ni alloys,stainless steel, gold, a gold alloy, palladium, carbon, silver, a noblemetal or a biocompatible material and any combination thereof.

The plurality of conductors may be arranged to form a resonator body.The resonator body may have a resonator body length, a resonator bodywidth and a resonator body depth. When an electrical signal is inducedthrough the resonator body, the electrical signal propagates through theconducting surface of skin depth. The electrical signal may be anelectrical current, an electrical voltage, a digital data signal or anycombination thereof.

The plurality of conductors in the resonator may comprise a firstconductor layer and a second conductor layer separated by an insulatorlayer wherein the first conductor layer is connected to the secondconductor layer or more by at least one connector. The conductor mayhave a cross-sectional shape, such as but not limited to a circularcross-section, a rectangular cross-section, a square cross-section, atriangular cross-section, or an elliptical cross-section. The resonatormay have a structural shape such as but not limited to a circularsolenoidal, a square solenoidal configuration, a circular spiralconfiguration, a square spiral configuration, a rectangularconfiguration, a triangular configuration, a circular spiral-solenoidalconfiguration, a square spiral-solenoidal configuration, or a conformalsolenoid configuration.

There is also disclosed a circuit for wireless transmission or wirelessreception. The circuit is designed to wirelessly transmit and/or receiveelectrical energy, electromagnetic energy, and electrical power. Inaddition, the circuit is capable of electronic data transmission.Furthermore, the circuit is capable of transmitting a combination ofelectrical energy, electromagnetic energy, electrical power andelectronic data together or separately.

Circuits at high frequencies extensively use passive elements such asinductors, capacitors, and the like. Some examples of such circuitconfigurations include but are not limited to band pass, high pass andlow pass filters; mixer circuits (e.g., Gilbert Cell); oscillators suchas Colpitts, Pierce, Hartley, and clap; and, amplifiers such asdifferential, push pull, feedback, and radio-frequency (RF).Specifically, inductors are used in matching and feedback in low noiseamplifiers (LNAs) as a source degeneration element. Lumped inductors arealso essential elements in RF circuits and monolithic microwaveintegrated circuits (MMICs). Lumped inductors are used in on-chipmatching networks where transmission line structures may be of excessivelength. Often, they are also used as RF chokes allowing bias currents tobe supplied to circuits while providing broad-band high impedance at RFfrequencies and above. RF MEMS switches, matching networks and varactorsthat are ideal for reconfigurable networks, antennas and subsystems alsoneed high Q inductors. Note, passive circuit element and lumped element,such as lumped inductor, may be used interchangeably with passivecircuit element being the broader term. The passive circuit element maybe an inductor, a capacitor, a resistor or just a wire. In nearly allthe above mentioned circuit examples, not meant to be limiting, it isdesired that the passive components are minimally lossy.

Given circuits at high frequencies extensively use passive elements suchas inductors and capacitors, an embodiment is given using but is notlimited to an inductor. Specifically considering an inductor, thedesigns should be such that maximum Q is attained while achieving thedesired inductance value. In other words, the resistive loss in theinductor needs to be minimized. Depending on the frequency of operation,available area on the substrate, the application and the technology, theinductor can be implemented as, but not limited to, a TEM/transmissionline, a conductive loop, or a spiral/solenoid/combination structure ofseveral shapes, for example, but not limited to, a circle, a rectangle,an ellipsoid, a square, or an irregular configuration. All theseembodiments, not meant to be limiting, may be realized using themulti-layer structure in the present invention.

In another example, a resonator as part of a larger circuit isdiscussed. A resonator is a device or a system that exhibits resonance(i.e., oscillates) at specific frequency, frequencies, or frequencyband(s), called the resonance frequency, frequencies, or frequencyband(s). At the resonance frequency, frequencies, or frequency band(s),there is minimum impedance to oscillation. In the context of electricalcircuits, there is minimum electrical impedance at the resonancefrequency, frequencies, or frequency band(s). The MLMT structure of thepresent invention may act as a resonator under two fundamentalconditions: (1) When the MLMT structure is designed to resonate at aspecific frequency, frequencies, or frequency band(s), in itsenvironment without any additional electrical components; (2) When theMLMT structure is designed to resonate at a specific frequency,frequencies, or frequency band(s), in its environment in combinationwith other components (for example, but not limited to, a capacitor, acapacitor bank, a capacitor and/or an inductor network). Thus, theresonator may be part of a larger circuit, and the resonance behaviormay be designed to occur at a frequency, frequencies, or frequencyband(s), or at a frequency, frequencies, or frequency band(s) with acertain bandwidth or certain bandwidths. Additional components (e.g.,resistance) may also be added to alter the bandwidth(s).

There is also disclosed a system for wireless transmission or wirelessreception. The system is designed to wirelessly transmit and/or receiveelectrical energy, electromagnetic energy, and electrical power. Inaddition, the system is capable of electronic data transmission.Furthermore, the system is capable of transmitting a combination ofelectrical energy, electromagnetic energy, electrical power andelectronic data together or separately.

The system may comprise a first resonator comprising a plurality offirst conductors, each first conductor having a first conductor length,a first conductor height, a first conductor depth, and a firstconductive surface having a first skin depth. The plurality of firstconductors may be arranged to form a first resonator body having a firstresonator body length, a first resonator body width and a firstresonator body depth. The system may also include a second resonatorcomprising a plurality of second conductors, each second conductorhaving a second conductor length, a second conductor height, a secondconductor depth, and a second conductive surface having a second skindepth. The plurality of second conductors may be arranged to form asecond resonator body having a second resonator body length, a secondresonator body width and a second resonator body depth. The first skindepth and the second skin depth may be approximately one-half of theconductor depth to about equal to the conductor depth. The first andsecond conductors may have at least one turn and each of the pluralityof first and second conductor layers may or may not have substantiallythe same conductor length, conductor height, and conductor depth. Thefirst conductor depth and the second conductor depth may be in the rangeof skin depth to twice the skin depth. However, depending on theavailable technology, costs, and application, the first conductor depthand the second conductor depth may be as large as twenty times or morethe skin depth. The first and second conductor layers may be formed froman electrically conductive material such as, but not limited to, copper,titanium, platinum and platinum/iridium alloys, tantalum, niobium,zirconium, hathium, nitinol, Co—Cr—Ni alloys, stainless steel, gold, agold alloy, palladium, carbon, silver, a noble metal or a biocompatiblematerial and any combination thereof.

When an electrical signal is propagated through the first resonatorbody, the electrical signal propagates through the first conductingsurface of skin depth and further induces an electrical signal throughthe second resonator body. The induced electrical signal propagatesthrough the second conducting surface at skin depth. The electricalsignal may be an electrical current, an electrical voltage, and adigital data signal, or combinations thereof.

The plurality of first conductors may comprise a first conductor layerand a second conductor layer separated by an insulator layer wherein thefirst conductor layer is connected to the second conductor layer or moreby at least one connector. The connector connecting the conductor layersmay be, but is not limited to, a via, a solder, a tab, a wire, a pin, ora rivet. The first conductor may have a first cross-sectional shape andthe second conductor may have a second cross-sectional shape. The firstand the second cross-sectional shapes are non-limiting and may be one ofa circular cross-section, a rectangular cross-section, a squarecross-section, a triangular cross-section, or an ellipticalcross-section.

The first resonator may have a first structural shape and the secondresonator may have a second structural shape. The first and the secondstructural shapes are non-limiting and may be a circular solenoidalconfiguration, a square solenoidal configuration, a circular spiralconfiguration, a square spiral configuration, a rectangularconfiguration, a triangular configuration, a circular spiral-solenoidalconfiguration, a square spiral-solenoidal configuration, or a conformalsolenoid configuration.

In addition, there is disclosed a method for manufacturing a structurefor wireless transmission or wireless reception. The method ofmanufacturing creates a structure that is capable of wirelesslytransmitting and/or receiving electrical energy, electromagnetic energy,and electrical power. In addition, the resulting structure is capable ofelectronic data transmission or reception. Furthermore, the resultingstructure is capable of transmitting and/or receiving a combination ofelectrical energy, electromagnetic energy, electrical power andelectronic data together or separately.

The method may comprise the steps of creating a plurality of conductorlayers having an insulator between each of the conductor layers andforming at least one connection between two of the plurality ofconductors. The connector connecting the conductor layers may be but isnot limited to a via, a solder, a tab, a wire, a pin, or a rivet. Theconductor layers may be created by depositing through a mask. The stepof creating a plurality of conductor layers having an insulator betweeneach of the conductor layers may further include the steps of placing afirst conductive layer on top of a second conductive layer andseparating the first conductive layer from the second conductive layerwith a first insulator. Further, the step of forming at least oneconnection between two of the plurality of conductors may include thesteps of connecting at least two of the conductive layers comprising butnot limited to a via, a solder, a tab, a wire, a pin, or a rivet. Theconductor layers may be formed from an electrically conductive material.The electrically conductive material may be comprised of copper,titanium, platinum and platinum/iridium alloys, tantalum, niobium,zirconium, hafnium, nitinol, Co—Cr—Ni alloys, stainless steel, gold, agold alloy, palladium, carbon, silver, a noble metal or a biocompatiblematerial and any combination thereof.

There is also disclosed a method for operating a structure to providewireless transmission or wireless reception. The method comprises thesteps of providing a structure that is capable of wireless transmissionand/or wireless reception of electrical energy, electromagnetic energy,and/or electrical power. In addition, the method provides the steps ofproviding a structure that is capable of electronic data transmission orreception. Furthermore, the method provides the steps of providing astructure that is capable of transmitting and/or receiving a combinationof electrical energy, electromagnetic energy, electrical power andelectronic data together or separately.

The method comprises the steps of providing a plurality of conductors,each conductor having a conductor length, a conductor height, aconductor depth, and a conductive surface having a skin depth. Further,the method comprises the steps of providing the skin depth to rangeapproximately one-half of the conductor depth to about equal to theconductor depth. The conductor depth may be in the range of skin depthto twice the skin depth. However, depending on the available technology,costs, and application, the conductor depth may be as large as twentytimes or more the skin depth. The plurality of conductors may bearranged to form a resonator body having a resonator body length, aresonator body width and a resonator body depth; and, inducing anelectrical signal in at least one of the plurality of conductors suchthat the electrical signal propagates through the conducting surface ofthe skin depth. The electrical signal may be an electrical current, anelectrical voltage, a digital data signal or any combination thereof.

The method may also include the step of providing a second plurality ofconductors, each of the second conductors having a second conductorlength, a second conductor height, a second conductor depth, and asecond conductive surface having a second skin depth wherein theplurality of second conductors are arranged to form a second resonatorbody having a second resonator body length, a second resonator bodywidth and a second resonator body depth. When an electrical signal ispropagated through the resonator body, the electrical signal propagatesthrough the conducting surface of the skin depth and further induces anelectrical signal through the second resonator body, and the inducedelectrical signal propagates through the second conducting surface atthe second skin depth.

The plurality of conductors may comprise a first conductor layer and asecond conductor layer separated by an insulator layer wherein the firstconductor layer is connected to the second conductor layer by at leastone connector. Further, the at least one connection connecting at leasttwo of the conductive layers comprises but is not limited to a via, asolder, a tab, a wire, a pin, or a rivet. The conductor may have across-sectional shape not limited to a circular cross-section, arectangular cross-section, a square cross-section, a triangularcross-section, and an elliptical cross-section. The plurality ofconductor layers may have at least one turn and each of the plurality ofconductor layers may or may not have substantially the same conductorlength, conductor height, and conductor depth. The conductor layer maybe formed from an electrically conductive material. The electricallyconductive material may be comprised of copper titanium, platinum andplatinum/iridium alloys, tantalum, niobium, zirconium, hathium, nitinol,Co—Cr—Ni alloys, stainless steel, gold, a gold alloy, palladium, carbon,silver, a noble metal or a biocompatible material or any combinationthereof.

The resonator may have a structural shape not limited to a circularsolenoidal configuration, a square solenoidal configuration, a circularspiral configuration, a square spiral configuration, a rectangularconfiguration, a triangular configuration, a circular spiral-solenoidalconfiguration, a square spiral-solenoidal configuration, and a conformalsolenoid configuration. Additional advantages and novel features will beset forth in part in the description which follows, and in part willbecome apparent to those skilled in the art upon examination of thefollowing and the accompanying drawings or may be learned by productionor operation of the examples. The advantages of the present teachingsmay be realized and attained by practice or use of various aspects ofthe methodologies, instrumentalities and combinations set forth in thedetailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawing figures depict one or more implementations in accord withthe present teachings, by way of example only, not by way of limitation.In the figures, like reference numerals refer to the same or similarelements.

FIG. 1 illustrates an AC current distribution for a steadyunidirectional current through a homogeneous conductor;

FIG. 2 illustrates an AC current distribution at increased frequency dueto skin effect;

FIG. 3 is a graph of skin depth vs. frequency;

FIG. 4 illustrates a high-level diagram of a structure for wirelesspower transfer;

FIG. 5A illustrates an example of an antenna in a circular solenoidalconfiguration;

FIG. 5B illustrates an example of an antenna in a square solenoidalconfiguration;

FIG. 5C illustrates an example of an antenna in a circular spiralconfiguration;

FIG. 5D illustrates an example of an antenna in a square spiralconfiguration;

FIG. 5E illustrates an example of an antenna in a multi-layer squarespiral configuration;

FIG. 5F illustrates an example of an antenna in a circularspiral-solenoidal configuration;

FIG. 5G illustrates an example of an antenna in a squarespiral-solenoidal configuration;

FIG. 5H illustrates an example of an antenna in a conformal solenoidconfiguration;

FIG. 6A illustrates an example of a single turn circular coil having Nlayers;

FIG. 6B illustrates an example of a double turn circularspiral-solenoidal coil of N layers;

FIG. 7A illustrates an example of an antenna having a circularcross-section;

FIG. 7B illustrates an example of an antenna having a rectangularcross-section;

FIG. 7C illustrates an example of an antenna having a squarecross-section;

FIG. 7D illustrates an example of an antenna having a triangularcross-section;

FIG. 7E illustrates an example of an antenna having an ellipticalcross-section;

FIG. 7F illustrates a rectangular cross-section of a multi-layer wire;

FIG. 8A illustrates a multi-layer wire having a circular cross-section;

FIG. 8B illustrates a multi-layer wire having a rectangularcross-section;

FIG. 9A shows a single turn antenna having 1 layer;

FIG. 9B shows a single turn antenna having 11 layers;

FIG. 9C shows a single turn antenna having 20 layers;

FIG. 9D shows a single turn antenna having 26 layers;

FIG. 10 is a graph illustrating the value of the quality factor as afunction of frequency;

FIG. 11A is a graph illustrating the relative changes in resistance andinductance with the number of layers;

FIG. 11B is a graph illustrating the resultant quality factor at 10 MHzfor the given number of layers;

FIG. 12A is a graph illustrating the quality factor as a function offrequency;

FIG. 12B is a graph illustrating the inductance relative to a 16 layercoil as a function of frequency;

FIG. 12C is a graph illustrating the resistance relative to the 16 layercoil as a function of frequency;

FIG. 13A is a graph illustrating the quality factor as a function offrequency;

FIG. 13B is a graph illustrating the inductance as a function offrequency;

FIG. 13C is a graph illustrating the resistance as a function offrequency;

FIG. 14A is a graph illustrating the quality factor as a function offrequency for a coil having a metal strip width of 1 mm;

FIG. 14B is a graph illustrating the relative increase in quality factorfor a coil having a metal width of 1.5 mm;

FIG. 14C is a graph illustrating the relative increase in quality factorfor a coil having a metal width of 2 mm;

FIG. 15 illustrates a high-level block diagram of a near-field energynetwork;

FIG. 16A illustrate a graph showing a situation where the receiving unitand transmitting unit have identical resonant frequencies the bandsnarrow;

FIG. 16B illustrates a graph showing a situation where the receivingunit and transmitting unit have different resonant frequencies the bandsnarrow;

FIG. 16C illustrates a graph showing a situation where the receivingunit and transmitting unit have different resonant frequencies and thereceiving unit has a wide resonant;

FIG. 16D illustrates a graph showing a situation where the receivingunit and transmitting unit have different resonant frequencies and thetransmitting device is lossy;

FIG. 16E illustrates a graph showing a situation where the receivingunit and the transmitting unit have resonant frequencies that are farapart and both the transmitting unit and the receiving unit are lossy;

FIG. 16F illustrates a graph showing a situation where the receivingunit and the transmitting unit have resonant frequencies that are closeand both the transmitting unit and the receiving unit are lossy;

FIG. 17 illustrates a high-level block diagram of a near-field energynetwork with repeaters;

FIG. 18 illustrates a typical PCB stackup;

FIG. 19 is a table of fabrication stack up for a 6-layer PCB board asobtained from an established PCB manufacturer;

FIG. 20 illustrates an equivalent circuit diagram of any MLMT structure;

FIG. 21 illustrates an equivalent circuit diagram for an MLMT structureoperating as an inductor (condition 1);

FIG. 22A illustrates an equivalent circuit diagram for an MLMT structureoperating as a self-resonator in a circuit (Type 1);

FIG. 22B illustrates an equivalent circuit diagram for an MLMT structureoperating as a stand alone self-resonator (Type 1);

FIG. 23A illustrates an equivalent circuit diagram for an MLMT structureshowing a capacitor addition in series;

FIG. 23B illustrates an equivalent circuit diagram for an MLMT structureshowing a capacitor addition in parallel;

FIG. 24A illustrates an equivalent circuit diagram for an MLMT structureoperating as a resonator in a circuit where resonance is achieved byadding a capacitor in parallel;

FIG. 24B illustrates an equivalent circuit diagram for an MLMT structureoperating as a stand alone resonator where resonance is achieved byadding a capacitor to the circuit in series;

FIG. 24C illustrates an equivalent circuit diagram for an MLMT structureoperating as a stand alone resonator where resonance is achieved byadding a capacitor to the circuit in parallel;

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth byway of examples in order to provide a thorough understanding of therelevant teachings. However, it should be apparent to those skilled inthe art that the present teachings may be practiced without suchdetails. In other instances, well known methods, procedures, components,and/or circuitry have been described at a relatively high-level, withoutdetail, in order to avoid unnecessarily obscuring aspects of the presentteachings.

The various technologies disclosed herein generally relate to methods,systems and apparatus to design, operate and manufacture wirelesstransmission and/or wireless reception systems, and more specifically,to methods, systems and apparatus to design, operate and manufacture ahigh efficiency structure for use in near-field wireless transmissionand/or reception.

Wireless transmission may embody wireless transmission of electricalenergy, electromagnetic energy, and electrical power such as theembodiments. In addition, wireless transmission may embody thetransmission of digital data and information. In a further embodiment, acombination of electrical energy, electromagnetic energy, electricalpower, electronic data and information may be transmitted together orseparately such as the embodiments discussed in energy networks. It isfurther contemplated that such wireless transmission could occur at thesame time or over a period of time intervals. Further embodiments ofwireless transmission are discussed in the energy networks, powernetworks, data networks and near-field power and data transfer systemsections below.

Wireless reception may embody wireless reception of electrical energy,electromagnetic energy, and electrical power such as the embodiments. Inaddition, wireless reception may embody the reception of digital dataand information. In a further embodiment, a combination of electricalenergy, electromagnetic energy, electrical power, electronic data andinformation may be received together or received separately such as theembodiments discussed in energy networks. It is further contemplatedthat such wireless reception could occur at the same time or over aperiod of time intervals. Further embodiments of wireless reception arediscussed in the energy networks, power networks, data networks andnear-field power and data transfer system sections below.

Wireless communication may embody wireless transmission and reception ofelectrical energy, electromagnetic energy, and electrical power such asthe embodiments. In addition, wireless communication may embody thetransmission and reception of digital data and information. In a furtherembodiment, a combination of electrical energy, electromagnetic energy,electrical power, electronic data and information may be transmitted andreceived together or transmitted and received separately such as theembodiments discussed in energy networks. It is further contemplatedthat such wireless transmission and reception could occur at the sametime or over a period of time intervals. Further embodiments of wirelesscommunication are discussed in the energy networks, power networks, datanetworks and near-field power and data transfer system sections below.

An antenna is generally a conductor by which electromagnetic waves aresent out or received. An antenna may consist of, but is not limited to,a wire or a set of wires. A resonator is generally any device ormaterial that resonates, including any system that resonates. Aresonator may be an instrument for detecting the presence of aparticular frequency by means of resonance, and may also be any circuithaving this frequency characteristic. Further, a resonator may be anelectrical circuit that combines capacitance and inductance in such away that a periodic electric oscillation will reach maximum amplitude.As appreciated by those skilled in the art, antennas often act asresonators when, for example, they self resonate or when they arecoupled with another reactive element such as a capacitor to achieveresonance. As such, the terms antenna and resonator are often usedinterchangeably herein, and are also referred to generically as astructure (e.g., multi-layer multi-turn structure).

“Skin effect” is generally the tendency for an alternating current toconcentrate near the outer part or “skin” of a conductor. As illustratedin FIG. 1, for a steady unidirectional current through a homogeneousconductor, the current distribution is generally uniform over the crosssection; that is, the current density is the same at all points in thecross section.

With an alternating current, the current is displaced more and more tothe surface as the frequency increases. This current does noteffectively utilize the full cross section of the conductor. Theconductor's effective cross section is therefore reduced so theresistance and energy dissipation are increased compared with the valuesfor a uniformly distributed current. In other words, as illustrated inFIG. 2, due to the skin effect, the current density is maximum near thesurface (also called the “skin”) of the conductor and decaysexponentially to the center of the cross-section.

The effective resistance of a wire rises significantly with frequency.In a preferred embodiment, this frequency may range from about 100 kHzto about 3 MHz and more preferably from about 3 MHz to about 10 GHz. Inan embodiment necessitating large antenna construction operating at 120KHz, it may even be beneficial to create a MLMT structure using largegauge wires/materials to achieve efficient performance.

For a copper wire of 1-mm (0.04-in.) diameter for example, theresistance at a frequency of 1 MHz is almost four times the dc value.“Skin depth” or “penetration depth” 6 is frequently used in assessingthe results of skin effect. It is generally accepted that the depthbelow the conductor surface at which the current density has decreasedto about 1/e (approximately 37%) of its value at the surface. The term“skin depth” is therefore described as the depth within thecross-section where the current density has dropped to about 37% of themaximum. This concept applies to plane solids, but can be extended toother shapes provided the radius of curvature of the conductor surfaceis appreciably greater than δ. For example, at a frequency of 60 Hz thepenetration depth in copper is 8.5 mm (0.33 in.); at 10 GHz it is only6.6×1⁰⁻⁷ m. The skin depth is a strong function of frequency anddecreases with increasing frequency. This phenomenon is displayed in thegraph shown in FIG. 3.

The fundamental concept of the multi-layer wire is to maximize theavailable current density over the full wire cross-section therebyreducing the wire's intrinsic resistance. By using a conductive layerwhose thickness is about twice the skin depth, it is ensured that thecurrent density at all points in the wire is greater than or equal to˜37% of the maximum possible current density (at surface). By usingother layer thicknesses, a different base current density will beobtained. For example, by using a layer thickness of about 4 times theskin depth, it will be ensured that current density is greater than orequal to ˜14% of the maximum possible current density (at surface).Similarly, for conductor depth approximately 6 times the skin depth, thecurrent density is greater than or equal to 5%.

While it is important to keep a high current density in the conductivelayers, at the same time, it is essential that the unusedcross-sectional area, i.e., the insulating layer, be as small aspossible overall. Using the above theory, an ideal proposedconfiguration for a multilayer wire includes conductive layers withthickness/depth about twice the skin depth, and an insulating layer, asthin as technologically possible. To those skilled in the art it will beunderstood that MLMT structures may result in embodiments wherein theskin depth, which is the conductive area active in wirelesscommunication, ranges from approximately one-half of the conductor depthto about equal to the conductor depth. On the other hand, givenlimitations imposed by some fabrication methods, designing MLMTstructures may also result in embodiments wherein the conductor depth,which is the area capable of conducting a signal but not necessarilyfully utilized as operating frequencies increase, ranges from skin depthto about twice the skin depth.

Wave-guide and resonant cavity internal surfaces for use at microwavefrequencies are therefore frequently plated with a high-conductivitymaterial, such as silver, to reduce the energy losses since nearly allthe current is concentrated at the surface. Provided the platingmaterial is thick compared to δ, the conductor is as good as a solidconductor of the coating material. “Quality factor” is generallyaccepted as an index (figure of measure) that measures the efficiency ofan apparatus like an antenna, a circuit, or a resonator. Via is definedherein as an electrically conductive connection from one layer toanother.

A Litz wire is generally a wire constructed of individual film insulatedwires bunched or braided together in a uniform pattern of twists andlength of lay.

Reference now is made in detail to the examples illustrated in theaccompanying drawings and discussed below. FIG. 4 illustrates ahigh-level diagram of a resonator for wireless power and/or datatransfer, such as an antenna. The resonator includes a coil 100 and amulti-layer wire 101. The shape of the coil 100 may be circular,rectangular, triangular, some other polygon, or conformal to fit withina constrained volume. FIG. 4 illustrates one exemplary configuration ofa coil in the form of a circular shaped coil 100. The configuration ofthe coil 100 may be solenoidal, spiral, or spiral-solenoid. A solenoidcoil follows a helical curve that may have multiple turns where eachturn has the same radius. A spiral coil configuration may have a numberof turns with a progressively increasing or decreasing radius. Aspiral-solenoidal coil configuration is a combination of a spiral andsolenoidal configuration. Other configurations known to those ofordinary skill may also be utilized to form the coil.

FIGS. 5A-5H illustrate examples of different antenna configurations thatmay be utilized. FIG. 5A illustrates an example of an antenna in acircular solenoidal configuration 102. FIG. 5B illustrates an example ofan antenna in a square solenoidal configuration 103. FIG. 5C illustratesan example of an antenna in a circular spiral configuration 104. FIG. 5Dillustrates an example of an antenna in a square spiral configuration105. It is understood that other spiral configurations, such asrectangular or triangular shape may also be utilized. FIG. 5Eillustrates an example of an antenna in a multi-layer square spiralconfiguration 106. It should be noted that although only two layers areillustrated in FIG. 5E, it is understood that any number of layers maybe used. As will be described below, when multiple layers are used, themultiple layers may be connected using but not limited to vias. solder,tabs, wires, pins, or rivets. In one embodiment, the plurality ofconductor layers less than or equal to the total number of layers, maybe connected electrically in parallel. Furthermore, in anotherembodiment, the plurality of conductor layers connected electrically inparallel may be connected electrically in series with one or more of aplurality of conductor layers connected electrically in parallel. Theseconnectors serve at least the following two purposes: (1) the connectorsconnect the layers of wire for the multi-layer wire; and (2) theconnectors connect one turn of the multi-layer wire to a second turn ofthe multi-layer wire. For example, a two-turn antenna then, there wouldbe at least one via from the first turn to the second turn. Otherpurposes may also be served by the connectors.

For each antenna, there exists an optimum number of connectors and anoptimum location for each connector. Since there is no closed-formanalytical solution for these, the optimal locations may best beobtained through iterative modeling. However, basic guidelines foroptimizing are given herewithin:

-   -   It is preferred that there be at least 2 connectors connecting        all of the layers that form a single conductor. These two        connectors will ideally be at the two ends of the multilayer        wire (the input and the output of the multilayer wire)    -   It is preferred the total number of connectors should be chosen        commensurate with the needs of a particular application. More        than the optimum number of connectors will increase current        paths which can lead to increased capacitance, increased        resistance, reduced quality factor and higher bandwidth. It        should also be noted that parasitic effects can become more        pronounced when the overall length (height, depth) of the        connector is greater than the optimum at a specific operating        frequency. The length of the connector in essence is the height        of the connector, and this should be kept smaller than about the        (effective wavelength)/20, though keeping it within        wavelength/10 could also lead to a workable embodiment,        depending on the application. The reason for these restrictions        is that the increased connector lengths will introduce        significant phase differences between the different layers of        the multilayer wire being used. These phase differences between        the different layers will introduce unwanted capacitive effects,        which will effectively lower self-resonance frequencies and        increase losses. It should be mentioned that, for embodiments in        which no additional components (for e.g. capacitors) are        utilized and the structure is being used as a self-resonant        resonator, connectors such as but not limited to vias with depth        higher than (effective wavelength)/10 might be incorporated in        the design of the antenna.

Vias can be of the form commonly used in printed circuit board (PCB)technologies (for example, through-hole, buried, blind) or thoseutilized in semiconductor or MEMS technology. Alternatively, the via canbe, but is not limited to, any conductive material that is laser-welded,welded, printed, soldered, brazed, sputtered deposited, wire-bonded andthe like in order to electrically connect at least any two layers and/orall layers.

FIG. 5F illustrates an example of an antenna in a circularspiral-solenoidal configuration 107. FIG. 5G illustrates an example ofan antenna in a square spiral-solenoidal configuration 108. FIG. 5Hillustrates an example of an antenna in a conformal solenoidconfiguration 109. The antenna in a conformal configuration may take theform of but is not limited to a circular or rectangular solenoid or acircular or rectangular spiral. Any of the antenna configurations shownin FIGS. 5A-5H may be used with the present system.

The coil 100 of FIG. 4 may have a plurality of turns 110. A turn may bebut is not limited to a bend, fold or an arc in the wire until the wirecompletes a revolution around the central axis point of the coil 111. Aturn may be in the same or similar shape of the coil configuration, suchas, for example, but not limited to a circle, a rectangle, a triangle,some other polygonal shape, or conformal to fit within a constrainedvolume. FIG. 6A illustrates a single turn circular coil having N layers,where “N” is a number equal to or greater than one. FIG. 6B illustratesa double turn circular solenoidal coil of N layers.

In general, for any inductive antenna, the inductance increases asT^(x), while the resistance increases as T^(y), where T is the number ofturns. In ideal conductors, x and y are 2 and 1 respectively. There areother factors which affect the inductance and resistance (hence thequality factor) which calls for x and y to be less than 2 and 1respectively. Referring to FIG. 13, three performance examples aregiven. The graph compares a 32 Layer-2 Turn antenna with a 32 Layer-1Turn antenna and a 64 Layer-1 Turn antenna. The inductance andresistance for the 32 Layer-2 Turn antenna increase between 3-3.5 timesand 1.7-3 times, respectively; over the 32 Layer-1 Turn antenna in thefrequency range 1 MHz-200 MHz. This increase is very near expectedvalues from simplistic analytical relations wherein resistance isapproximately T; and inductance is approximately T².

The multi-layer wire 101 in FIG. 4 may have but is not limited to acircular, rectangular, square, or triangular cross-sectional shape. Inaddition, other shapes known to those of ordinary skill may also beutilized. FIGS. 7A-7E illustrate examples of cross-sections of wiresthat may be used in the design of an antenna. FIG. 7A illustrates anexample of an antenna having a circular cross-section 401. FIG. 7Billustrates an example of an antenna having a rectangular cross-section402. FIG. 7C illustrates an example of an antenna having a squarecross-section 403. FIG. 7D illustrates an example of an antenna having atriangular cross-section 404. FIG. 7E illustrates an example of anantenna having an elliptical cross-section 405. FIG. 7F illustrates arectangular cross-section of a multi-layer wire having a firstconductive layer 410 and a second conductive layer 420. In addition tothe embodiments discussed above, the multi-layer wire 101 may becomprised of a rigid wire structure, a fixed flexible wire structure ora combination thereof.

An insulating material 430 separates the first layer 410 from the secondlayer 420. The first layer 410 and second layer 420 are connected withvias 440 which traverse the insulating material 430. The conductivelayers 410, 420 may be layers of conductive tape/ribbon/sheet/leaf ordeposited metal having a metal thickness and metal strip width. Themetal thickness of the first layer 410 is identified by line A-A and themetal strip width of the first layer 410 is identified by line B-B. Inone example, the metal thickness of a layer may be approximately twicethe skin depth. The skin depth may range from approximately one-half ofthe conductor depth to about equal to the conductor depth Each layer ina turn will have substantially the same metal thickness and metal stripwidth.

The thickness of the insulating material may be sufficient to meet theneeds of the application or equal to the minimum thickness possible bythe available fabrication technology. Additionally, the overallstructure feasibility depends on the frequency of operation (as shown inthe graph of FIG. 1), associated costs and fabrication technologyutilized. Generally in PCB technology, the thickness of layers isdictated by the “core thickness” and the pre-preg thickness. In otherdesigns, the thickness of the non-conducting layer is selected to modifythe electrical behavior of a structure.

Typical PCB stackup comprises alternating layers of the core and thepre-preg. The core generally comprises a thin piece of dielectric withcopper foil bonded on both sides. The core dielectric is generally curedfiberglass-epoxy resin. The pre-preg is generally uncuredfiberglass-epoxy resin. The pre-preg will cure (i.e., harden) whenheated and pressed. The outermost layers are generally pre-preg withcopper foil bonded to the outside (surface foils). Stackup is generallysymmetric about the center of the board in the vertical axis to avoidmechanical stress in the board under thermal cycling as shown in FIG.18.

One embodiment wherein the conductor and insulating layer thicknessesare equal to the minimum thickness possible by the available fabricationtechnology is given for an application at 13.56 MHz. At 13.56 MHz, theskin depth is about 17.8 micrometers. Ideally, the conductor depthshould be about 35.6 micrometers and the insulation thickness should beas small as possible. As shown in FIG. 19, however, in actuality, usinga PCB fabrication method with standard, established, low costtechniques, the fabrication stack up obtained for a 6-layer PCB board isabout 71 micrometers which is nearly 4 times the skin depth. Further,the insulating layer is more than 3 times the conductive layer. AdvancedPCB techniques, which come at a significantly higher cost, may allow alower conductor and insulation depth. For example, PCB techniquescurrently in the research stage, could allow the conductive materiallike copper as low as 5 micrometers and the insulating dielectric about39 micrometers. Other techniques, such as semiconductor fabrication andMEMS fabrication techniques could allow much thinner layer thicknessleading to performance that is nearer to ideal. If semiconductor or MEMSfabrication is used, the thicknesses of both the conducting layers andthe insulating layers may be as thin as a few 100 nanometers or eventhinner. In a preferred embodiment, the dielectric layer thickness isless than 200 micrometers and as perfectly insulating as possible, andwith a permittivity lower than 10.

Similarly, the dielectric layer could be made from several materials,and can be of various configurations. For example, some applications mayrequire extremely low parasitic capacitance. In such cases, anon-conducting dielectric with the lowest possible permittivity ispreferred. Additionally, it may be desired to increase the insulatinglayer thickness to minimize the parasitic effects. Another example wouldbe for applications that might require ferrite materials to increaseinductance and/or increase magnetic shielding. In such cases, thedielectric layers might be replaced by a ferrite film/block or similarpropertied configuration/material.

It will be apparent to one skilled in the art, therefore, that theinsulating material will be of a thickness such that the thickness iswithin the practical capabilities of the manufacturing technology usedto manufacture that resonator and compatible with the efficiency needsof the application for which the resonator is intended.

The material of the conductive layers may be copper or gold, however,other materials are possible. To enhance conductivity, copper or goldwith a layer of deposited silver may also be used. In the case where theantenna is implanted and may be exposed to body fluids, then thetypically known biocompatible materials should be utilized, includingadditions for enhancing conductivity. These may include, but are notlimited to, conductive material taken from the group of: titanium,platinum and platinum/iridium alloys, tantalum, niobium, zirconium,hathium, nitinol, Co—Cr—Ni alloys such as MP35N, Havar®, Elgiloy®,stainless steel, gold and its various alloys, palladium, carbon, or anyother noble metal. Depending on the application, the insulating materialmay be (i) air, (ii) a dielectric with a low permittivity (such as, forexample, Styrofoam, silicon dioxide, or any suitable biocompatibleceramic), (iii) a non-conductive dielectric with a high permittivity,(iv) a ferrite material, or (v) a combination of the materials listedabove. The choice of material or combination of materials may resultfrom factors such as the fabrication process, cost and technicalrequirements. For example, if a high capacitive effect is required toaffect a lower self-resonance frequency of an antenna, a highpermittivity dielectric might be preferred, or, a combination ofmaterials including a ferrite film or ferrite block might be preferredto increase the self-inductance of the antenna. In addition, the use ofa ferrite core may be used to provide increased performance.

FIG. 8A-FIG. 8B illustrate examples of different multi-layer wirecross-sectional configurations. FIG. 8A illustrates a multi-layer wirehaving a circular cross-section 510. FIG. 8B illustrates a multi-layerwire having a rectangular cross-section 520. In FIG. 8B, the via 530that connects the conductive layers 540 is positioned at the port orinput 550, which is the beginning of the wire. Depending on the specificapplication, the positioning of the vias 530 that connect the conductivelayers may impact the performance of the antenna. For example,insufficient vias may lead to phase differences between the differentlayers. Conversely, an abundance of vias may lead to additional cyclicalcurrent paths that may increase the resistive loss. The vias may belocated at the beginning of the wire (e.g., port, input, etc), or at oneor more locations along the wire. Additionally, the vias between one setof two or more conductive layers may be at a different location thananother set of two or more conductive layers. It is understood thatseveral variations may be possible depending on the application and thesystem design. The via can be made using techniques standard to thetechnology being utilized for the fabrication of the multi-layermulti-turn structure. In other cases, the vias can be implemented usingsoldering techniques, such as, by connecting the several layers at vialocations using electric solder, welded tabs, laser weld tacking, orother commonly known electrical connecting techniques.

As will be described herein, the antenna is preferably designed with ahigh quality factor (QF) to achieve efficient transfer of power thatreduces intrinsic resistive losses of the antenna at high frequencies.The quality factor is the ratio of energy stored by a device to theenergy lost by the device. Thus, the QF of an antenna is the rate ofenergy loss relative to the stored energy of the antenna. A sourcedevice carrying a time-varying current, such as an antenna, possessesenergy which may be divided into three components: 1) resistive energy(W_(res)), 2) radiative energy (W_(rad)), and 3) reactive energy(W_(rea)). In the case of antennas, energy stored is reactive energy andenergy lost is resistive and radiative energies, wherein the antennaquality factor is represented by the equationQ=W_(rea)/(W_(res)+W_(rad)).

In near field communications, radiative and resistive energies arereleased by the device, in this case the antenna, to the surroundingenvironment. When energy must be transferred between devices havinglimited power stores, e.g., battery powered devices having sizeconstraints, excessive power loss may significantly reduce the devices'performance effectiveness. As such, near-field communication devices aredesigned to minimize both resistive and radiative energies whilemaximizing reactive energy. In other words, near-field communicationsbenefit from maximizing Q.

By example, the efficiency of energy and/or data transfer betweendevices in an inductively coupled system is based on the quality factorof the antenna in the transmitter (Q1), the quality factor of theantenna in the receiver (Q2), and the coupling coefficient between thetwo antennas (κ). The efficiency of the energy transfer varies accordingto the following relationship: eff∞κ²·Q₁Q₂. A higher quality factorindicates a lower rate of energy loss relative to the stored energy ofthe antenna. Conversely, a lower quality factor indicates a higher rateof energy loss relative to the stored energy of the antenna. Thecoupling coefficient (κ) expresses the degree of coupling that existsbetween two antennas.

Further, by example, the quality factor of an inductive antenna variesaccording to the following relationship: Q=2πfL/R where f is thefrequency of operation, L is the inductance, and R is the totalresistance (ohmic+radiative). As QF is inversely proportional to theresistance, a higher resistance translates into a lower quality factor.

A higher quality factor may be achieved using multiple layers in amulti-layer wire for a single turn of coil. Increasing the number ofturns in a coil may also be used to increase the quality factor of thestructure. For a design at a constant frequency, there may be an optimumnumber of layers to reach a maximum quality factor. Once this maxima isreached, the quality factor may decrease as more layers are added. Thedesign variables that may be used for the multi-layer multi-turnstructure include:

-   -   a. Metal strip width, w_(n) (e.g. w₁: width of the 1^(st)        conductive layer, w_(k): width of the k^(th) conductive layer).        Also referred to as metal width or strip width    -   b. Number of conductive layers per turn, N₁, (e.g. number of        layers in 1^(st) turn, N₁)    -   c. Thickness of each conductive layer, d₁, (e.g. d₁: thickness        of 1^(st) layer, d_(k): thickness of k^(th) layer)    -   d. Thickness of insulation, di_(n) (e.g. di₁: thickness of        insulation under 1^(st) layer, di_(k): thickness of insulation        under k^(th) layer)    -   e. Number of turns, T    -   f. Number of vias connecting the different conductive layers in        each turn    -   g. Location of vias connecting the different conductive layers        in each turn    -   h. Shape (circular, rectangular, some polygon; depends on the        application; for e.g. could be conformal to fit just outside or        just inside some device or component)    -   i. Configuration: solenoidal, spiral, spiral-solenoidal, etc)    -   j. Dimensions (length, width, inner radius, outer radius,        diagonal, etc.)

Below, exemplary multi-layer multi-turn designs based on the aboveparameters will be described.

In one example, the antenna may be a single turn circular coil havingmulti-layer wire, as illustrated in FIGS. 9A-9D. The single turn coilincludes a single turn and may include a metal strip width ofapproximately 1.75 mm, a metal thickness of approximately 0.03 mm, aninsulating layer of approximately 0.015 mm, and an outer radius ofapproximately 5 mm. The wire may have between 5 and 60 layers, such as5, 11, 20, 26, 41, or 60 layers. For example, FIG. 9A shows a singleturn antenna having 1 layer, FIG. 9B shows a single turn antenna having11 layers, FIG. 9C shows a single turn antenna having 20 layers, andFIG. 9D shows a single turn antenna having 26 layers. Although specificexamples are shown in FIGS. 9A-9D, it is understood that the wire mayhave less than 5 or more than 60 layers in order to achieve a highquality factor. The corresponding coil thickness for the range of 5 to60 layers may be between approximately 0.2 mm to 3 mm, such as forexample, 0.2, 0.5, 1, 1.25, 2.05, or 3 mm, respectively. As mentionedabove, it is understood that by varying the number of layers in thewire, the number of turns, the metal thickness, and the metal stripwidth, a higher quality factor may be obtained. For example, for a 1layer single turn coil having a metal thickness of 0.03 mm and a metalstrip width of 1.75 mm, the quality factor at 10 MHz is approximately80. Increasing the number of layers from 1 to 11 and keeping a metalthickness of 0.03 mm and a metal strip width of 1.75 mm, the qualityfactor is increased to approximately 210. Generally, an increase in thenumber of layers per turn results in an increase in quality factor untilmaxima is reached, after which the quality factor starts to decrease.This decrease may occur when the total height of the antenna becomescomparable to its radius. With electrical components, the degradationstarts due to greatly increased parasitic effects due to the multiplelayers (e.g. capacitance and proximity effects). In the present example,increasing the layers to 20, 26, 41 and 60 results in quality factors ofapproximately 212, 220, 218 and 188, respectively.

To demonstrate benefits of the present teachings vis-à-vis the prior artsolutions, models of the present teachings were developed to comparewith known coils. The prior art models were assumed to be made usingsolid wire. For a circular coil with radius r; wire radius, a; turns, N;inductance (L) and resistance (R_(ohmic) and R_(radiation)) as given bythe following equations:

$L = {\mu_{0}N^{2}r\; {\ln \left\lbrack {\left( \frac{8r}{a} \right) - 2} \right\rbrack}}$$R_{ohmic} = \sqrt{\frac{\mu_{0}\rho \; \omega}{2}\frac{Nr}{2}}$$R_{radiation} = {\frac{\pi}{6}\eta_{0}{N^{2}\left( \frac{\omega \; r}{c} \right)}^{4}}$

Two antenna configurations were considered, the specifics of which areprovided in the Table 1 and Table 2 below. The results indicate that thepresent teachings allow for significantly higher QF's than the solidwire. The performance improvement shown herein applies when other knownmethods of construction are utilized.

TABLE 1 Antenna Configuration-1 Using above Inductance ResistanceQuality Factor formula IE3D (numerical) L_(formula) L_(numerical)R_(formula) R_(numerical) Q_(formula) Q_(numerical) 1 turn 1-turn 30 nH28.7 nH 0.0583 0.0337 1225 2034 R = 1 cms R = 1 cms A (wire radius) = 1mm Strip width ~1 mm Wire area ~3.14 mm² Layer f = 380 MHz thick. ~0.01mm Total thick. ~2.5 mm Total wire area ~2.5 mm² MLMT design 1 turn1-turn 30 nH   9 nH 0.0583 0.0083 1225 2671 R = 1 cms R = 0.5 cms A(wire radius) = 1 mm Strip width ~1 mm Wire area ~3.14 mm² Layer f = 380MHz thick. ~0.01 mm Total thick. ~2 mm Total wire area ~2 mm² MLMTdesign

TABLE 2 Antenna Configuration-2 Using above Inductance ResistanceQuality Factor formula IE3D (numerical) L_(formula) L_(numerical)R_(formula) R_(numerical) Q_(formula) Q_(numerical) 1 turn 1 turn  830nH 1.16 μH 0.0815 0.0498 1161 2489 R = 15 cms R = 15 cms (wire radius) =2 mm Strip width ~2 mm Wire Layer thick ~0.03 mm area ~12.5 mm² TotalThick ~1 mm f = 17 MHz Total wire area ~2 mm² MLMT design 1 turn 1 turn1.92 μH 2.48 μH 0.1854 <0.08 1105 >2500 R = 30 cms R = 30 cms (wireradius) = 2 mm Strip width ~3 mm Wire Layer thick ~0.03 mm area ~12.5mm² Total Thick ~1 mm f = 17 MHz Total wire area ~3 mm² MLMT design

It is also understood that the metal strip width may be increased toachieve a higher quality factor. FIG. 10 provides a graph of the valueof the quality factor as a function of frequency. FIG. 11A is a graphillustrating the relative changes in resistance and inductance with thenumber of layers. FIG. 11B illustrates the resultant quality factor at10 MHz. It should be noted that with regard to FIGS. 11A-B, the datapoints on the graph correspond as data point 1 is for 1 layer, datapoint 2 is for 11 layers, data point 3 is for 20 layers, data point 4 isfor 26 layers, data point 5 is for 41 layers, and data point 6 is for 60layers. To ensure signal flow through all layers of the structure, it ispreferable that at least two vias be included for any multi-layer wireand/or structure. These two vias are preferably located at the ports ofthe wire/structure. As can be seen from FIGS. 10 and 11A-B, optimalperformance for 10 MHz is achieved for an antenna configuration having26 layers and 1 turn. For this antenna configuration, the peak qualityfactor is obtained around 35 MHz and is approximately 1100.

In another example, the antenna may be a single turn circular coil ofmulti-layer wire and may have a metal strip width of approximately 1 mm,a metal thickness of approximately 0.01 mm, an insulating layer ofapproximately 0.005 mm, and an outer radius of approximately 5 mm. Thewire may have between 16 and 128 layers, such as 16, 32, 64, or 128layers. However it is understood that the wire may have less than 16 ormore than 128 layers in order to achieve a high quality factor. Thecorresponding coil thickness for the range of 16 to 128 layers may bebetween approximately 0.25 mm to 2 mm, such as for example, 0.25, 0.5,1, or 2 mm, respectively. In this example, the quality factor improveswith increasing the number of layers, with larger quality factorsachieved at higher frequencies. For example, at a frequency of 10 MHz,the quality factor for 16, 32, 64 and 128 layers is approximately 127,135, 140 and 185, respectively. The peak quality factor increases tonearly 2900 at approximately 450 MHz under these design parameters. Therelative resistance may be lowest around the frequency at which theconductor thickness is about twice the skin depth. In this example, thatfrequency is 160 MHz.

FIGS. 12A-C are graphs illustrating the performance parameters andtrends. FIG. 12A is a graph illustrating the quality factor as afunction of frequency. FIG. 12B is a graph illustrating the inductancerelative to a 16 layer coil as a function of frequency. FIG. 12C is agraph illustrating the resistance relative to the 16 layer coil as afunction of frequency. As can be seen in FIG. 12A, the quality factorimproves with an increasing number of layers with relatively largerquality factors at higher frequencies. This is further shown in FIGS.12B-C where it is shown that where the inductance is relatively constant(as compared to a 16 layer 1 turn coil) with frequency, while theresistance decreases as frequency increases as shown by the troughsaround 100 MHz in FIG. 12C. The peak quality factor goes up toapproximately 2900 at around 450 MHz.

In yet another example, all design parameters are the same as in thepreceding example for a 32 layer wire, except the number of turns isdoubled, resulting in a double turn circular coil. The inductance andresistance for this 32 layer, double turn antenna increase between 3-3.5times and 1.7-3 times, respectively, over the 32 layer, single turnantenna in the frequency range of 1 MHz to 200 MHz. FIGS. 13A-C aregraphs illustrating the performance parameters and trends for this 32layer, double turn antenna compared to the 32 and 64 layer, single turnantennas in the preceding example. FIG. 13A is a graph illustrating thequality factor as a function of frequency. FIG. 13B is a graphillustrating the inductance as a function of frequency. FIG. 13C is agraph illustrating the resistance as a function of frequency. As can beseen in FIGS. 13A-C, for the 32 layer, double turn antenna atfrequencies below about 200 MHz, the inductance is nearly constant andthe resistance follows trends similar to the single turn antennas. Atfrequencies greater than 200 MHz, both the inductance and resistancerise rapidly due to the contribution of parasitic capacitance, which isexplained below. Even though the quality factor remains high atfrequencies greater than 200 MHz, there may be significant electricfields present due to the capacitive effect, which may not be acceptablein some applications.

As noted above, an antenna may display parasitic effects. Associatedwith the antenna is a parasitic capacitance that is frequency dependentand whose contribution to the overall impedance increases withfrequency. As a result of the parasitic capacitance, there exists aself-resonance frequency for the antenna beyond which the antennabehaves like a capacitor. To prevent the onset of parasitic capacitance,the antenna may be designed such that the inductance is nearlyunchanging around the frequency of operation. Preferably, the slope ofthe reactance versus frequency graph is nearly linear (around thefrequency of operation) with slope, ∂X/∂ω˜L (where X is the reactance,and L is the inductance that was designed for). Operating the antenna inthis regime ensures that the parasitic coupling via electric fields iskept to a minimum. It is understood that that the X versus ω may not beperfectly linear due to other effects such as current crowding,proximity and skin effects.

It is also contemplated that other designs may be used for the antennain order to achieve higher quality factors. For example, for a singleturn circular coil of multi-layer wire that may have between 16 and 128layers, such as 16, 32, 64, or 128 layers, the coil may include a metalstrip width of approximately 1 mm, a metal thickness of approximately0.01 mm, an insulating layer of approximately 0.01 mm, and an outerradius of approximately 10 mm. Increasing the width of the metal reducesthe resistance and the inductance, resulting in a higher quality factor.Due to the overall large size of the antenna (outer radius ˜10 mm), therelatively small increase in the width (w) does not reduce theinductance. It should be noted that the same increase in metal width fora smaller antenna, such as, for example, with outer radius approximately5 mm, the decrease in inductance would have been higher. FIGS. 14A-C aregraphs illustrating the quality factors as a function of frequency forthis example with a metal strip width of approximately 1 mm, 1.5 mm and2 mm, respectively. In this example, the quality factor at 379 MHz isapproximately 1425 for a metal strip width of 1 mm. Increasing the metalstrip width to 1.5 mm and 2 mm increases the quality factor toapproximately 1560 and 1486, respectively.

It should be noted that all the QF values mentioned above for theinductors are in free space (conductivity=0, relative permittivity=1).It is expected that the presence of a real world environment will affectthe QF. For example, an antenna with a QF ˜400 in free space, could havethe QF change to about 200-300 when it is placed next to the human body.Further, if the antenna is placed inside the human body with little orno insulating coating, the QF might further change to less than 200.Applying a coating sufficiently thick or enclosing in a sufficientlylarge package before placing inside the human body might decrease thechange in the QF of the antenna. It is expected that similar changes inQF characteristics will occur in any medium and in the proximity of anymaterial, with the deviation from free space depending on the electricalproperties of the material/medium and the distance from it.

As will be discuss herein, utilization of near-field communication forwireless transmission and/or reception can be applied to energy, poweror data networks.

Energy Networks

An energy transfer network may be developed according to the presentteachings. FIG. 15 illustrates a high-level block diagram of anear-field energy network 10. The network 10 includes a plurality ofdevices 11 _(a-d) (generally referred to as device 11). Each device 11may include a transceiver. The transceiver may include a transmittingunit 12 _(a-d) and a receiving unit 14 _(a-d) for wirelesscommunications. Although each transceiver may include a transmittingunit 12 and a receiving unit 14, it is understood that the transceivermay comprise only a transmitting unit 12 or only a receiving unit 14.Further, it is understood that the transmitting unit 12 and thereceiving unit 14 in the transceiver may share certain or all circuitelements or may have separate and distinct circuit elements. Further,the transmitting unit 12 and/or receiving unit 14 may be coupled to aload 16. The load 16 may comprise of components within the device 11,outside the device 11, or a combination of components within and outsidethe device 11.

Each transmitting unit 12 includes a transmitting antenna 13. Thetransmitting antenna 13 has a resonant frequency w and preferably hasminimal resistive and radiative losses. The load 16 may include drivercircuitry to generate signals to drive the transmitting antenna 13.Based on the received signals, the transmitting antenna 13 may produce anear-field in all directions (omni-directional) or may produce anear-field targeted towards a specific direction (directional). Thetargeted near-field may be produced through shielding, such as byferrite materials. Of course, it is understood to those skilled in theart that other materials may be used to provide targeted near-fields.

Each receiving unit 14 includes a receiving antenna 15. A single antennamay be used for both the receiving antenna 15 and the transmittingantenna 13 or a separate antenna may be used for the receiving antenna15 and the transmitting antenna 13. Each antenna 13, 15 has a resonantfrequency (referred to as ω_(a)-ω_(d)). If separate transmitting andreceiving antenna are used, it is preferred that the resonant frequencyof the receiving antenna 15 is equal to the resonant frequency of thetransmitting antenna 13.

When a receiving unit 14 of one device 11 (e.g., receiving unit 14 _(b)of device 11 _(b)) is placed in the near-field of the transmitting unit12 of another device 11 (e.g., transmitting unit 12 _(a) of device 11_(a)), an electromagnetic field generated by the transmitting unit 12_(a) will interact with the receiving unit 14 _(b). If the resonantfrequency of a receiving unit 14 (e.g., receiving unit 14 _(b) of device11 _(b) having resonant frequency ω_(b)) is the same as the resonant ofthe transmitting unit 12 (e.g., transmitting unit 14 _(a) of device 11_(a) having resonant frequency ω_(a)), the reactive electromagneticfields of the transmitting unit 11 a will induce an alternating currentwithin the receiving unit 14 _(b). The induced current may be used toprovide power or convey data to load 16 _(b). As a result, device 11_(b) is able to absorb energy from device 11 _(a). It is understood thatany number of devices having a resonant frequency equal to theresonating frequency of the transmitting device (e.g., ω_(b)) may beadded to the near-field energy network and draw energy from thetransmitting device, provided that the resonant frequency of thetransmitting unit 12 _(a) is not significantly altered due to theloading effect of the added devices.

If the resonant frequency of a receiving unit 14 (e.g., receiving unit14, of device 11, having resonant frequency ω_(c)) is different than theresonant of the transmitting unit 12 (e.g., transmitting unit 12 _(a) ofdevice 11 _(a) having resonant frequency ω_(a)), the receiving unit 14_(c) will have a high impedance to the transmitting unit 12 _(a) andwill draw little energy from the transmitting unit 12 _(a).

It is understood that the amount of energy transferred from atransmitting unit 12 _(a) to receiving unit 14 _(c) depends on manyfactors, including intrinsic losses in the transmitting unit 12 _(a) andreceiving unit 14 _(c) and the transfer of energy to other devices suchas receiving unit 14 _(b). Also significant are the proximity of ω_(a)and ω_(c) and the width of the resonant bands in each device. FIGS.16A-F illustrates graphs showing how various factors affect the transferof energy.

FIG. 16A illustrates a situation where ω_(a) and ω_(c) are identical andthe bands narrow. This represents an ideal scenario and the case ofmaximum power transfer efficiency. FIG. 16B illustrates a situationwhere ω_(a) and ω_(c) are different and the bands narrow. No energy istransferred in this scenario. FIG. 16C illustrates a situation whereω_(a) and ω_(c) are different and receiving unit 14 _(c) has a wideresonant. A wider resonant band occurs when an antenna has higherresistive and radiative losses. Receiving unit 14 _(c) has moreimpedance to ω_(a) than in the situation shown in FIG. 16B, but is stillable to absorb some energy from transmitting device 11 _(a). FIG. 16Dillustrates a situation where ω_(a) and ω_(c) are different andtransmitting device 11 _(a) is lossy. Resistive and radiative losses intransmitting device 11 _(a) lead to a wide resonant band. A smallerportion of the antennas energy is available for transfer to receivingunit 14 _(c). FIG. 16E illustrates a situation where ω_(a) and ω_(c) arefar apart and both the transmitting unit 12 _(a) and the receiving unit14 _(c) are lossy. Here, no energy is transferred from the transmittingunit 12 _(a) to the receiving unit 14 _(c). FIG. 16F illustrates asituation where ω_(a) and ω_(c) are close and both the transmitting unit12 _(a) and the receiving unit 14 _(c) are lossy. Energy is transferredbetween the transmitting unit 12 _(a) and the receiving unit 14 _(c) butthe system is inefficient due to high losses.

Many common everyday objects are conductive (e.g., steel cabinets, andautomobiles) and will have frequency responses similar to receiving unit14 _(c) in FIG. *16C (but wider because of greater resistive losses).These objects are thus able to absorb some energy from transmitting unit12 _(a) and contribute to losses in the system. Thus far, only thegeneral transfer of energy has been discussed, however, the use of theenergy may vary by application, but broadly may be for either thetransfer of power or the transfer of data.

Power Networks

A power transfer network may be developed according to the presentteachings. When a receiving unit 14 _(b) is placed within the near-fieldof a transmitting unit 12 _(a) and the resonant frequency of thereceiving unit 14 _(b) (i.e., ω_(b)) is approximately equal to theresonant frequency of the transmitting unit 12 a (ω_(a)), energy willtransfer from the transmitting unit 12 _(a) to the receiving unit 14_(b). If multiple receiving devices (e.g., 11 _(b)-11 _(d)), all havinga resonant frequency equal to the resonant frequency of the transmittingunit 12 _(a) (i.e., ω_(a)), are placed in the near-field, each receivingdevice (e.g., 11 _(b)-11 _(d)) will draw energy from the transmittingunit 12 _(a) in the form of an alternating current. The receivingdevices 11 _(a)-11 _(d) may include a transducer which may use theinduced alternating current to store energy in a power storage device,such as battery or capacitor. Alternatively, the transducer may useinduced alternating current to directly power electronic componentswithin or couple to the receiving device (e.g., 11 _(b)-11 _(d)).

It is understood that it may not be possible to place all transmittingand receiving devices (e.g., 11 _(b)-11 _(d)) within the near-field ofthe transmitting unit 12 _(a). As illustrated in FIG. 17, in order todeliver energy to receiving devices 11 outside of the near-field (e.g.,receiving unit 11 _(c)) one or more repeaters 18 may be used. The one ormore repeaters 18 may contain an antenna 20 which is tuned to ω_(a). Therepeater 18 may draw energy from the transmitting unit 12 via theantenna 20 in the form of an induced current. The one or more repeaters18 may use the induced current to produce a second energy field usingthe antenna 20. Alternatively, the second energy field may be producedusing a second antenna (not shown). The second energy field may be usedto induce an alternating current in the receiving unit 14 _(c). Thereceiving unit 14 _(c) may include a transducer which may use theinduced alternating current to store energy in a power storage device,such as battery or capacitor. Alternatively, the transducer may useinduced alternating current to power electronic components within thereceiving unit 14 _(c). It is understood that the antenna 20 or secondantenna (not shown) may produce a near-field in all directions(omni-directional) or may produce a near-field targeted towards aspecific direction (directional).

Data Networks

A data transfer network may be developed according to the presentteachings. A network designed for data transfer would be similar to thepower networks described previously, except that the signal transmittedby the transmitting devices in the network may be modulated time-varyingsignals which carry data. There are several possible general layouts fora data-network.

One example of a data network layout includes one or more receivingunits (14 _(b-d)) placed within the near-field of a transmitting unit 12_(a). Each of the receiving units (14 _(b-d)) may be capable ofcommunicating to the transmitting unit 12 a and/or other receiving units14. It is understood that receiving units which may be out of near-fieldof the transmitting unit 12 may be reached using one or more repeaters18 in the manner described above. In another example, a receiving unit14 may be placed far-field of the transmitting unit 12 and utilize theradiative field of the transmitting unit 12 for communication. Suchfar-field communication is achieved in a manner similar to far-fieldcommunication techniques known to those of ordinary skill in the art.

The devices 11 within the networks may be designed to handledata-transfer in several ways. For example, the devices 11 and theirantennas 13, 15 may be designed to (1) receive data only; (2) transmitdata only; or (3) receive and transmit data, using either a sharedantenna for receiving and transmitting or separate and dedicatedantennas for receiving and transmitting. In addition, the devices 11 maybe designed to handle both data- and power-transfer. In such situations,each device 11 may be designed to: (1) transfer data only; (2) transferpower only; (3) transfer data and power, where each device 11 may useany combination of sending/receiving data and sending/receiving power,each device 11 has a shared antenna for data- and power-transfer, oreach device 11 has separate, dedicated antennas for data- andpower-transfer.

Each receiving unit 14 may have an electronic identification (ID) thatis unique to that receiving unit 14 on the network 10. The ID acts as anidentifier for a particular receiving unit 14 on the network and allowsa receiving unit 14 on the network to identify other receiving units 14on the network 10 for communication. To initiate a data-transfersession, a transmitting device would identify a receiving device withits ID and begin communications using an initiation instruction. Thedata transfer would occur using a specified modulation scheme. Securityprotocols may be used to ensure that the data transferred by and storedin the devices are secure and not accessible to unauthorized deviceswhich are not present in the designed network 10.

Periodic data communication may occur between a transmitting unit 12 andone or more receiving units 14 or between a receiving unit 14 and one ormore other receiving units 14. In transmitting unit-receiving unitcommunications, a transmitting unit 12 may identify a particularreceiving unit 14 based on its ID and initiate a communication session.Alternative, a receiving unit 14 may identify a transmitting unit 12based on its ID and initiate a communication session. The communicationsession may be terminated by either the transmitting unit 12 or thereceiving unit 14.

In receiving unit-receiving unit communications, two receiving units 14may connect directly with each other in direct communication.Alternatively, two receiving units 14 may connect with each other usingthe transmitting unit 12 as an intermediary. In such cases, eachreceiving unit 14 may connect to the transmitting unit 12 and thetransmitting unit 12 would receive information from one receiving unit14 and transmit it to the other receiving unit 14. In anotheralternative, two receiving units 14 may communicate using one or morerepeaters 18 where the one or more repeaters 18 may receive a signalfrom a receiving unit 14 and transmit it to another receiving unit 14.The one or more repeaters 18 may be one or more stand-alone resonantantennae and may be independent of any circuitry.

The system and method illustrated in FIG. 15 and FIG. 17 to efficientlytransfer energy between two or more devices may be used in a variety ofapplications in order to operate household appliances such as vacuums,irons, televisions, computer peripheral devices; mobile devices;military applications such as surveillance equipment, night visiondevices, sensor nodes and devices; transportation applications such assensors designed to monitor automobile or train performance and safety;aerospace applications, such as control of flaps, rudders, or landinggear; space technology; naval applications such as applications to powerunmanned watercraft; traffic control applications such as road imbeddedsensors; industrial applications; asset tracking such as RFID tags andtransponders; robotic networks; and medical devices.

General Near-Field Power and Data Transfer System

As appreciated by the present teachings, near-field power and datatransfer are derived from the same physical principles. When utilizedtogether, near-field power and data transfer provide an opportunity tocreate a wide variety of systems. The following describes a generalsystem for near-field power and data transfer.

An near field power and data network (also referred herein as a“NF-PDAT”) may consist of multiple transmitting and receiving units. Forthe sake of simplicity, a simpler network consisting of a singletransmitting unit 12 and a single receiving unit 14 is considered. Thefollowing description follows the path of the energy as it istransferred from the transmitting unit 12 to the receiving unit 14 andto a load coupled to the receiving unit 14.

Initially, the energy needed to drive the PDAT network must be obtainedfrom a primary source. The primary source may be a main 50/60 Hz wallsocket, a standard battery, a rechargeable battery connectable to a wallsocket, or a rechargeable battery with indirect recharging. Awall-socket is one preferred method of obtaining energy because of itsabundance in this form. In the event a device cannot be connected a wallsocket, or portability is a requirement, batteries may be used. Inaddition, rechargeable batteries may be used. Rechargeable batteries maybe replenished when their stored energy falls below a capacity. It isknown that recharging allows batteries to be sued in devices that wouldotherwise drain batteries too quickly, have too little space forbatteries of an appropriate size, or have limited access for replacingthe battery. A primary source of power, such as a wall socket or anotherbattery may be used to replenish battery life in the rechargeablebattery. In most devices, recharging is typically accomplished byconnecting the battery to a wall socket for a short period of time(e.g., laptops and cell-phones). In some applications (e.g., implantedmedical devices), direct attachment to a power cord is not possible. Insuch situations, indirect recharging methods, such as inductive couplingto an external power source, have been used. It is understood thatrecharging may be accomplished by other methods. For example, if thereexists a clear line-of-sight between the energy source and the device,an optical link, laser, or highly-directive radio-frequency beam may beused to transfer energy.

Alternative sources of energy may be used to power the system or toprovide energy for components within the system (such as recharging abattery). These may include the conversion of one form of energy intoelectrical energy. One such example is the conversion of kinetic energyinto electrical energy. This may be accomplished by converting movementinto energy. For instance, a device attached to the body may use bodymovements to spin a rotor that causes a generator to produce analternating current. Another example is the conversion of light energyinto electrical energy. For instance, photovoltaic cells placedexternally may convert sunlight or ambient room light into energy. Inanother example, changes in pressure may be converted into electricalenergy. For instance, a piezoelectric appropriately placed on a devicemay be used to convert pressure changes (e.g. air pressure changes ordirect pressure through contact) into electrical currents. In anotherexample, thermal gradients may be converted into electrical energy. Forinstance, a thermo-electric generator (TEG) placed within a device maybe used to convert a temperature gradient across the device intoelectrical energy. Such a TEG may be useful in devices that produce heatduring their operation, as a portion of the heat energy could beconverted into electrical energy.

The present teachings also include a method for designing a multi-layermulti-turn antenna for use in a high efficiency wireless power and datatelemetry system. Given a certain frequency of operation, one or more ofthe following steps may be followed to design application-specificantennae:

-   -   1. Perform analytical calculations and system level simulations        to obtain minimum required inductance for sufficient coupling        coefficient    -   2. Based on analytical calculations (e.g., for coupling        coefficient, induced voltage, etc), choose the number of turns        required for the appropriate inductance    -   3. Select the conductor layer thickness to be about 2 times the        skin depth or the minimum allowable based on the fabrication        technology; whichever is higher.    -   4. Select the insulation thickness to be the minimum allowable        by the fabrication technology or a larger thickness to achieve        desired performance.    -   5. Select the maximum surface area possible (depends on the        application). This area need not necessarily be square or        circular. It could be any shape conforming to the overall system        and could meander around other components.    -   6. Select the maximum number of layers possible depending on        fabrication technology and the application.    -   7. Design a multi-layer multi-turn antenna in a numerical        modeling tool (e.g., based on MoM or FDTD or FEM or MLFMM OR        some other or combination of these) with the number of turns        from step-1 and 2, and optimize (Steps 3-6) the number of layers        and other parameters.        -   a. Ensure that the Quality factor peak is obtained in the            whereabouts of the selected frequency        -   b. Ensure that the inductance for this quality factor is            greater than or equal to the minimum allowable (from system            level constraints)        -   c. If required, ensure that the E-fields are minimized by            keeping the parasitic capacitive effects low (refer to            previous section)

The present teachings also include a method of manufacturing the antennaafter the antenna is designed. The multi-layer multi-turn antennautilizes strips of metal that may be deposited through a specific maskin, for example but not limited to, a PCB/ceramic/metal printing processor in a semiconductor foundry. An alternative method of fabricating theantenna may utilize conductive tape/ribbon/sheet/leaf with one or moretape/ribbon/sheet/leaf placed on top of each other separated by aninsulating layer and shorting the multiple strips by soldering at thedesignated via locations. Another method of fabricating the antennawould be to cut out specific shapes from conductive sheets or “leaf”(for e.g. gold or copper leaf) and following steps that similar to thatfor the conductive tape/ribbon. A three dimensional printing process(such as that offered by Eoplex Technologies) may also be used inaddition to metal deposition processes like physical vapor deposition,thin film deposition, thick film deposition and the like.

The present teachings lends itself to be incorporated with currentfabrication techniques for multi-layer printed wiring board, printedcircuit boards and semiconductor fabrication technologies withmulti-layer interconnects. As advancements in fabrication techniques aremade, it is expected that the multi-layer multi-turn antenna will likelybenefit greatly from such improvements. This compatibility withconventional fabrication techniques will allow these antennas to berelatively easily incorporated into conventional circuit boards. Suchadvances may also provide accurate repeatability and small feature sizes(i.e., high resolution).

As noted above, the design and structure of the present system allowsfor extended range (i.e., the separation distance between a transmittingand a receiving wireless antenna). The increase in range enables powerto be transferred across a greater distance, allowing the transmitter tobe further away from the receiver. For example, in applications such asRFID, the tag read range for high frequency interrogators is no greaterthan 3 feet, which is insufficient for certain applications, such aspallet tracking. The wireless antenna of the present system offers animprovement for pallet tracking via RFID by delivering the concentratedpower that this particular application requires to facilitate reflectingthe interrogator signal needed for better extended read rangeperformance. In other applications such as military systems, theextended range provided by the present invention enables transfer ofpower to devices in difficult to reach locations, or to devices in harshenvironments. In consumer electronics the extended range allows for theuser to charge or transfer energy to a device from a more convenientlocation.

The present system also enables multiple operational needs from a singledesign concept, namely, the multi-layer multi-turn antenna. The presentsystem may serve as a receiver antenna, a source antenna, a transceiver(acting as a source and a receiver), and as a repeater antenna.Alternatively, the design may be used for inductor designs solely as alumped element in a circuit (e.g., in RF filters circuits, RF matchingcircuits).

The MLMT antenna structure of the present invention may be representedin various circuit design embodiments. An equivalent circuit diagram forthe MLMT antenna structure is given in FIG. 20. It comprises thefollowing parameters:

-   -   L_(M)=Intrinsic Inductance    -   C_(M)=Intrinsic Capacitance    -   R_(M)=Intrinsic Resistance

The characteristics of the MLMT antenna embodiment depend on the designvalues of L_(M), R_(M), and C_(M); the operating center frequency andadditional components that are placed across Terminal 1 and Terminal 2.

Let the angular frequency of operation be w. The input impedance,Z_(input) of the MLMT antenna embodiment then is given in general termsby equation 1(c) based on 1(a) and 1(b)

$\begin{matrix}{{Z\; 1} = \frac{1}{j \cdot \omega \cdot C_{M}}} & {{Equation}\mspace{14mu} 1(a)} \\{{Z\; 2} = {R_{M} + {j \cdot \omega \cdot L_{M}}}} & {{Equation}\mspace{14mu} 1(b)} \\{Z_{input} = \frac{Z\; {1 \cdot Z}\; 2}{{Z\; 1} + {Z\; 2}}} & {{Equation}\mspace{14mu} 1(c)}\end{matrix}$

The MLMT antenna structure of the present invention then can berepresented in various circuit design embodiments. For example, the MLMTantenna structure can be operated in three modes:

-   -   Mode 1: as an inductor such as embodied in a lumped circuit        element, when condition 1, which is given by equation 2(a), is        satisfied resulting in equation 2(b). The equivalent circuit        diagram is given in FIG. 21.

Z1>>Z2  Equation 2(a)

Z _(input) ≈Z2  Equation 2(a)

-   -   Mode 2: as a resonator such as embodied in a stand-alone tank        circuit or embodied in an HF and/or RF circuit, where the        resonator may be one of two types        -   Type 1: as a self-resonator, when condition 2, given by            equation 3 is satisfied. The equivalent circuit diagrams are            given in FIGS. 22A and 22B

ω² ·L _(M) ·C _(M)≈1  Equation 2(a)

-   -   -   Type 2: as a resonator, where resonance is achieved by            adding a capacitor, C_(ADDED) in series or parallel. The            equivalent circuit diagrams showing series and parallel            capacitor additions are given in FIGS. 23A and 23B. The Mode            2 Type 2 circuit diagrams are given in FIGS. 24A, 24B, and            24C.        -   In both Type 1 and Type 2, L_(pickup) and L_(feed) refer to            a pickup inductor and a feed inductor, respectively. These            are coils which have an inductance that is smaller than the            inductance value of the MLMT structure, L_(M), and have a            certain coupling to the MLMT structure. The coupling may be            varied to achieve the desirable matching conditions for            power transfer to or from the MLMT structure from or to the            rest of the system. For simplicity and proof of concept, the            embodiments described herein provide a single capacitor,            C_(ADDED) example for achieving resonance for illustration            purposes. In a practical circuit, a more complex circuit            comprising multiple capacitors and/or inductors and/or            resistors may be used. All embodiments shown in FIGS. 22 and            24 may be used on the transmitter side and/or on the            receiver side of the system.

    -   Mode 3: as a capacitor, when condition 3, given by equation 4 is        satisfied

ω² ·L _(M) ·C _(M)>1  Equation 4

The unique arrangement of the layers and customized wire segmentation inthe present system compared with existing design technologiesdemonstrates improved system performance in similar and smallerpackaging volumes as shown by quality factors that are more than 2 timeshigher than those realized from existing technologies. By combiningmaterial with specific properties, specifying shapes, lengths, andthicknesses and defining layer order, the present system permits pairingof the inductance and quality factor with a specific application tooptimally achieve a desired response, including, but not limited to,wireless tissue stimulation, wireless telemetry, wireless componentrecharging, wireless non-destructive testing, wireless sensing, andwireless energy or power management.

Another specific advantage of the present system is that it enables amore efficient means of Near Field Magnetic Coupling (NFMC) for powerand/or data transfer in an equivalent or smaller design volume byreducing conductor loss associated with increasing frequencies (due tothe phenomenon referred to as Skin Effect). The proposed system alsoprovides a solution that can be relatively easily achieved by existingmanufacturing techniques (for example multi-layer printed wiring board),and can therefore be integrated with other circuit components such asICs, resistors, capacitors, surface mount components, etc. Otheradvantages of the present system includes reducing power consumptionthereby leading to longer battery lives (where applicable), a reductionin the Joule heating of the antenna, decreasing the consumption ofenvironmental resources of the appliance/device, and any other benefitderived from a more energy efficient device.

Other applications that may benefit from these wireless systems includebut are not limited to geo-sensing, oil exploration, fault detection,portable electronic, military, defense and medical devices, among othermedical implantable, medical non-implantable, commercial, military,aerospace, industrial and other electronic equipment or deviceapplications. It is understood that the scope of the invention coversnot only any application that will benefit from increases in efficiency,but also any application that may require the use of an inductiveelement.

While the foregoing has described what are considered to be the bestmode and/or other examples, it is understood that various modificationsmay be made therein and that the subject matter disclosed herein may beimplemented in various forms and examples, and that the teachings may beapplied in numerous applications, only some of which have been describedherein. It is intended by the following claims to claim any and allapplications, modifications and variations that fall within the truescope of the present teachings.

What is claimed is:
 1. A system for wireless communication comprising: afirst resonator comprising a plurality of first conductors, each firstconductor having a first conductor length, a first conductor height, afirst conductor depth, and a first conductive surface having a firstskin depth wherein the plurality of first conductors are arranged toform a first resonator body having a first resonator body length, afirst resonator body width and a first resonator body depth; a secondresonator comprising a plurality of second conductors, each secondconductor having a second conductor length, a second conductor height, asecond conductor depth, and a second conductive surface having a secondskin depth wherein the plurality of second conductors are arranged toform a second resonator body having a second resonator body length, asecond resonator body width and a second resonator body depth; wherein afirst electrical signal is propagatable through the first resonator bodyand the first conducting surface of the first skin depth, and a secondelectrical signal is further inducible through the second resonatorbody, and the second electrical signal is propagatable through thesecond conducting surface of the second skin depth.
 2. The system ofclaim 1 wherein the plurality of first conductors comprises a firstconductor layer and a second conductor layer separated by an insulatorlayer wherein the first conductor layer is connected to the secondconductor layer by at least one connector.
 3. The structure of claim 2wherein at least one of plurality of the first and the second conductorlayers comprises at least one of a conductive tape, a conductive ribbon,and a deposited metal.
 4. The system of claim 1 wherein the firstconductor has a first cross-sectional shape and the second conductor hasa second cross-sectional shape, the first and second cross-sectionalshapes comprising at least one of a circular cross-section, arectangular cross-section, a square cross-section, a triangularcross-section, and an elliptical cross-section.
 5. The system of claim 1wherein at least one of the first and the second electrical signalcomprises at least one of an energy signal, a power signal, and a datasignal.
 6. The system of claim 1 wherein at least of the first and thesecond electrical signal comprises at least one of an electricalcurrent, an electrical voltage, and a digital data signal.
 7. The systemof claim 1 wherein the first and the second electrical signals may besubstantially the same.
 8. The system of claim 1 wherein the first skindepth range from about one-half to about equal of the first conductordepth and the second skin depth range from about one-half to about equalof the second conductor depth.
 9. The system of claim 1 wherein thefirst conductor depth range from the first skin depth to twice the firstskin depth and the second conductor depth range from the second skindepth to twice the second skin depth.
 10. The system of claim 1 whereinthe first conductor depth is greater than about twice the first skindepth and the second conductor depth is greater than about twice thesecond skin depth.
 11. The system of claim 1 wherein the plurality offirst and second conductors has at least one turn.
 12. The system ofclaim 1 wherein each of the plurality of first and second conductors hassubstantially the same conductor length, conductor height, or conductordepth.
 13. The system of claim 1 wherein the first resonator has a firststructural shape and the second resonator has a second structural shape,the first and the second structural shapes comprising at least one of acircular solenoidal configuration, a square solenoidal configuration, acircular spiral configuration, a square spiral configuration, arectangular configuration, a triangular configuration, a circularspiral-solenoidal configuration, a square spiral-solenoidalconfiguration, and a conformal solenoid configuration.
 14. The system ofclaim 1 wherein at least one of the first and the second conductors areformed from an electrically conductive material.
 15. The system of claim14 wherein the electrically conductive material includes at least one ofcopper, titanium, platinum and platinum/iridium alloys, tantalum,niobium, zirconium, hathium, nitinol, Co—Cr—Ni alloys, stainless steel,gold, a gold alloy, palladium, carbon, silver, a noble metal, and abiocompatible material.
 16. The system of claim 1 wherein at least oneinsulator is formed from an electrically insulative material.
 17. Thesystem of claim 16 wherein the electrically insulative material includesat least one of air, Styrofoam, silicon dioxide, a biocompatible ceramicor any similar dielectric with a low permittivity, a non-conductivedielectric with a high permittivity, and a ferrite material.
 18. Thesystem of claim 1 wherein the first electrical signal is induciblethrough the first resonator body at a frequency selected from afrequency range from about 100 kHz to about 3 MHz and the secondelectrical signal are inducible through the second resonator body at afrequency selected from a frequency range from about 100 kHz to about 3MHz.
 19. The system of claim 18 wherein the frequency is a frequencyband that is within a frequency range from about 100 kHz to about 3 MHz.20. The system of claim 1 wherein the first electrical signal isinducible through the first resonator body at a frequency selected froma frequency range from about 3 MHz to about 10 GHz and the secondelectrical signal is inducible through the second resonator body at afrequency selected from a frequency range from about 3 MHz to about 10GHz.
 21. The system of claim 20 wherein the frequency is a frequencyband that is within a frequency range from about 3 MHz to about 10 GHz.22. The system of claim 1 having a quality factor greater than
 100. 23.The system of claim 1 further comprising a circuit element selected froma group consisting of a resistor, an inductor and a capacitor.
 24. Thesystem of claim 1 further incorporatable within a device comprising atleast one of a resonator, an antenna, an RFID tag, an RFID transponder,and a medical device.